The present invention relates to electrolytes circulation type metal-halogen batteries and in particular to improvements in metal-bromine secondary batteries of the type employing bromine as a positively active material.
More particularly, the invention relates to a secondary battery in which a complexing agent is added to the anode electrolyte storage tank such that particularly the bromine molecules in the electrolyte form a bromic complex compound to separate in a diphasic manner in the lower part of the electrolyte or even if the complexing agent does not unite with the bromine, the complexing agent does not dissolve into the electrolyte or does not easily dissolve into the electrolyte to separate from the electrolyte in a diphasic manner, thus effectively maintaining the electrolyte in the desired condition and preventing the self-discharge and/or increase in the battery internal resistance and thereby making the electrolyte storage tank compact and high in safety.